Communication systems are known in which optical signals, each being modulated to carry data and having a different wavelength, are transmitted from a first location to a second location. The optical signals may be combined on a single fiber and transmitted to a receiving node that includes circuitry to optically separate or demultiplex each signal. Alternatively, coherent detection techniques may be employed to extract the data carried by each optical signal.
In such systems, a plurality of transmitters may be provided, such that each transmitter supplies a respective one of the optical signals. Typically, each transmitter includes a laser, modulator, and associated circuitry for controlling the modulator and the laser. As network capacity requirements increase, however, additional transmitters may be provided to supply additional optical signals, but at significantly increased cost.
Moreover, communications systems may include multiple nodes, such that selected optical signals may be intended to transmission to certain nodes, and other signals may be intended for reception by one or more other nodes. Accordingly, optical add-drop multiplexers (“OADMs”) may be provided to drop one or more signals at an intended local receiver, for example, while other optical signals are passed by the OADM to one or more downstream nodes. Further, optical signals may be added by the OADM for transmission to one or more nodes in the communication system. Thus, the optical signals may be transmitted over varying distances and through varying numbers of OADMs. In addition, the data and/or baud rate, and or modulation format is preferably tailored to a particular route, as well as the capacity of the intended receiver.
Thus, not only may multiple transmitters be required to provide a required number of optical signals to satisfy network capacity needs, but each transmitter may be required to be customized to generate each optical signal with a desired modulation format, data rate, and/or baud rate.